Accessory Middle Cerebral Artery Originating from the Posterior Circulation, Presenting with an Occult Ruptured Cerebral Aneurysm: a Case Report—Management of Atypical Subarachnoid Haemorrhage Cases with Rare Vascular Variations

An accessory middle cerebral artery (aMCA) is a rare anatomical variation which has been linked to cerebrovascular aneurysms. There has never been an aMCA with a posterior circulation origin reported in the literature. We present a case report of a posterior circulation aMCA and a concomitant ruptured native MCA bifurcation aneurysm. Initial workup was non-diagnostic but clinical suspicion, and the existence of this rare variation orientated our management towards an exploratory craniotomy. A blister aneurysm was recognized on the native M1 bifurcation and was clipped with a single clip. Patients with rare vascular variations should be aggressively investigated for cerebrovascular aneurysms. Especially when there is clinical suspicion, further workup or even exploration is warranted.